The present invention is directed to polypeptides related to vascular endothelial cell growth factor (hereinafter sometimes referred to as VEGF) and bone morphogenetic protein 1 (hereinafter sometimes referred to as bmp 1), termed herein as VEGF-E polypeptides, nucleic acids encoding therefor, methods for preparing VEGF-E, and methods, compositions and assays utilizing VEGF-E.
Polypeptides involved in survival, proliferation and/or differentiation of cells are of interest. Polypeptides known to be involved in the survival, proliferation and/or differentiation of cells include VEGF and members of the bone morphogenetic protein family. Therefore, novel polypeptides which are related to either VEGF or the bone morphogenetic protein are of interest.
The heparin-binding endothelial cell-growth factor, VEGF, was identified and purified from media conditioned by bovine pituitary follicular or folliculo-stellate cells over several years ago. See Ferrara et al., Biophys. Res. Comm. 161, 851 (1989). VEGF is a naturally occurring compound that is produced in follicular or folliculo-stellate cells (FC), a morphologically well characterized population of granular cells. The FC are stellate cells that send cytoplasmic processes between secretory cells.
VEGF is expressed in a variety of tissues as multiple homodimeric forms (121, 165, 189 and 206 amino acids per monomer) resulting from alternative RNA splicing. VEGF121 is a soluble mitogen that does not bind heparin; the longer forms of VEGF bind heparin with progressively higher affinity. The heparin-binding forms of VEGF can be cleaved in the carboxy terminus by plasmin to release (a) diffusible form(s) of VEGF. Amino acid sequencing of the carboxy terminal peptide identified after plasmin cleavage is Arg110-Ala111. Amino terminal xe2x80x9ccorexe2x80x9d protein, VEGF (1-110) isolated as a homodimer, binds neutralizing monoclonal antibodies (4.6.1 and 2E3) and soluble forms of FMS-like tyrosine kinase (FLT-1), kinase domain region (KDR) and fetal liver kinase (FLK) receptors with similar affinity compared to the intact VEGF165 homodimer.
As noted, VEGF contains two domains that are responsible respectively for binding to the KDR and FLT-1 receptors. These receptors exist only on endothelial (vascular) cells. As cells become depleted in oxygen, because of trauma and the like, VEGF production increases in such cells which then bind to the respective receptors in order to signal ultimate biological effect. The signal then increases vascular permeability and the cells divide and expand to form new vascular pathwaysxe2x80x94vasculogenesis and angiogenesis.
Thus, VEGF is useful for treating conditions in which a selected action on the vascular endothelial cells, in the absence of excessive tissue growth, is important, for example, diabetic ulcers and vascular injuries resulting from trauma such as subcutaneous wounds. Being a vascular (artery and venus) endothelial cell growth factor, VEGF restores cells that are damaged, a process referred to as vasculogenesis, and stimulates the formulation of new vessels, a process referred to as angiogenesis.
VEGF would also find use in the restoration of vasculature after a myocardial infarct, as well as other uses that can be deduced. In this regard, inhibitors of VEGF are sometimes desirable, particularly to mitigate processes such as angiogenesis and vasculogenesis in cancerous cells.
Regarding the bone morphogenetic protein family, members of this family have been reported as being involved in the differentiation of cartilage and the promotion of vascularization and osteoinduction in preformed hydroxyapatite. Zou, et al., Genes Dev. (U.S.), 11(17):2191 (1997); Levine, et al., Ann. Plast. Surg., 39(2):158 (1997). A number of related bone morphogenetic proteins have been identified, all members of the bone morphogenetic protein (BMP) family. Bone morphogenetic native and mutant proteins, nucleic acids encoding therefor, related compounds including receptors, host cells and uses are further described in at least: U.S. Pat. Nos. 5,670,338; 5,453,419; 5,661,007; 5,637,480; 5,631,142; 5,166,058; 5,620,867; 5,543,394; 4,877,864; 5,013,649; 5,106,748; and 5,399,677. Of particular interest are proteins having homology with bone morphogenetic protein 1, a procollagen C-proteinase that plays key roles in regulating matrix deposition.
The present invention is predicated upon research intended to identify novel polypeptides which are related to VEGF and the BMP family, and in particular, polypeptides which have a role in the survival, proliferation and/or differentiation of cells. While the novel polypeptides are not expected to have biological activity identical to the known polypeptides to which they have homology, the known polypeptide biological activities can be used to determine the relative biological activities of the novel polypeptides. In particular, the novel polypeptides described herein can be used in assays which are intended to determine the ability of a polypeptide to induce survival, proliferation or differentiation of cells. In turn, the results of these assays can be used accordingly, for diagnostic and therapeutic purposes. The results of such research is the subject of the present invention.
The objects of this invention, as defined generally supra, are achieved at least in part by the provision of a novel polypeptide, VEGF-E, (SEQ ID NO:2) and the nucleic acid encoding therefor, SEQ ID NO:1, residues 259 through 1293.
In one embodiment, the invention provides an isolated nucleic acid molecule comprising DNA encoding a VEGF-E polypeptide. In one aspect, the isolated nucleic acid comprises DNA encoding the VEGF-E polypeptide having amino acid residues 1 through 345 of FIG. 2 (SEQ ID NO:2), or is complementary to such encoding nucleic acid sequence, and remains stably bound to it under low stringency conditions. In another embodiment, variants are provided wherein the VEGF-E nucleic acid has single or multiple deletions, substitutions, insertions, truncations or combinations thereof.
In another embodiment, the invention provides a vector comprising DNA encoding a VEGF-E polypeptide. A host cell comprising such a vector is also provided. By way of example, the host cells may be 293 transient cells, bacculovirus infected insect cells, CHO cells, E. coli, or yeast. A process for producing VEGF-E polypeptides is further provided and comprises culturing host cells under conditions suitable for expression of VEGF-E and recovering VEGF-E from the cell culture.
In another embodiment, the invention provides isolated VEGF-E polypeptide. In particular, the invention provides an isolated native sequence VEGF-E polypeptide, which in one embodiment, includes an amino acid sequence comprising residues 1 through 345 of FIG. 2 (SEQ ID NO:2). In another embodiment, variants are provided wherein the VEGF-E polypeptide has single or multiple deletions, substitutions, insertions, truncations or combinations thereof.
In another embodiment, the invention provides chimeric molecules comprising a VEGF-E polypeptide fused to a heterologous polypeptide or amino acid sequence. An example of such a chimeric molecule comprises a VEGF-E polypeptide fused to an epitope tag sequence or a Fc region of an immunoglobulin.
In another embodiment, the invention provides an antibody which specifically binds to a VEGF-E polypeptide. Optionally, the antibody is a monoclonal antibody.
In yet further embodiments, the present invention is directed to compositions useful for treating indications where proliferation, survival and/or differentiation of cells is desired, comprising a therapeutically effective amount of a VEGF-E polypeptide hereof in admixture with a pharmaceutically acceptable carrier.
The invention further includes associated embodiments of VEGF-E such as modified VEGF-E polypeptides and modified variants which have the same biological applications as VEGF-E, and pharmaceutical compositions incorporating same. Inhibitors of VEGF-E are also provided.